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Web service
A Web service is a method of communications between two electronic devices over the World Wide Web. It is a software function provided at a network address over the web with the service always on as in the concept of utility computing. The W3C defines a Web service as: }} The W3C also states: , in which the primary purpose of the service is to manipulate XML representations of Web resources using a uniform set of stateless operations; and * , in which the service may expose an arbitrary set of operations. }} Web API .|325x325px]] A web API is a development in web services where emphasis has been moving to simpler representational state transfer (REST) based communications. RESTful APIs do not require XML-based web service protocols (SOAP and WSDL) to support their interfaces. Automated design methods Automated tools can aid in the creation of a web service. For services using WSDL, it is possible to either automatically generate WSDL for existing classes (a bottom-up model) or to generate a class skeleton given existing WSDL (a top-down model). * A developer using a bottom-up model writes implementing classes first (in some programming language), and then uses a WSDL generating tool to expose methods from these classes as a web service. This is simpler to develop but may be harder to maintain if the original classes are subject to frequent change. * A developer using a top-down model writes the WSDL document first and then uses a code generating tool to produce the class skeleton, to be completed as necessary. This model is generally considered more difficult but can produce cleaner designs and is generally more resistant to change. As long as the message formats between sender and receiver do not change, changes in the sender and receiver themselves do not affect the web service. The technique is also referred to as contract first since the WSDL (or contract between sender and receiver) is the starting point. Web services that use markup languages There are a number of web services that use markup languages: *JSON-RPC *JSON-WSP *Web template *Web Services Description Language (WSDL) from the W3C *XML Interface for Network Services (XINS) provides a POX-style Web service specification format *Web Services Conversation Language (WSCL) *Web Services Flow Language (WSFL) (superseded by BPEL) *WS-MetadataExchange *Representational state transfer (REST) versus remote procedure call (RPC) *XML-RPC - XML - Remote Procedure Call Criticisms Critics of non-RESTful web services often complain that they are too complex and based upon large software vendors or integrators, rather than typical open source implementations. There are also concerns about performance due to web services' use of XML as a message format and SOAP/HTTP in enveloping and transporting. See also *Service-oriented architecture (SOA) *List of web service specifications *List of web service protocols *List of web service frameworks References External links *Messaging Design Pattern and a distributed component/service model *W3C Web Services Activity home page *Web Services Architecture (W3C Working Group Note) *Where to find Web Services on the Web: Investigating Web Services on the World Wide Web (2008) *NIST SP800-95 Guide to Secure Web Services *Webzesty Pvt.Ltd. - Website Designing Company in India Category:Web services